Understanding Repulsion‐Governed Adsorption Mechanism for Efficient Surface Passivation in Blade‐Coated Perovskite Solar Cells

Surface passivation of perovskite thin‐films via adsorption of amine‐based derivatives plays an important role in minimizing nonradiative recombination. In this work, we developed a novel and efficient amine‐based surface passivation molecule, cystamine dihydrochloride (CH), which possesses a characteristic symmetric structure and exhibits an anomalous passivation mechanism. It is found that the electron‐rich sulfur atoms in central disulfide moiety of CH experience strong short‐range repulsion with surface iodides of perovskites. Consequently, contrary to the conventional attraction‐driven‐based passivation mechanism, the presence of S–I repulsion dictates a unique binding geometry that drives preferential coordination of the two terminal amine groups with undercoordinated Pb 2+ while displacing sulfur atoms away from the surface. This repulsion‐induced interfacial reconstruction effectively suppresses the formation of deep‐trap Pb–Pb dimers and thereby significantly suppresses nonradiative recombination. Eventually, the blade‐coated PSCs with CH‐passivated achieve a champion efficiency of 26.15% compared to 23.64% of the control devices, along with markedly improved operational stability. This work provides new insight into repulsion‐mediated interfacial passivation for high‐efficiency and stable perovskite solar cells.